In recent years, an increase in capacity has been demanded in a non-volatile memory for data storage. The non-volatile memory for data storage is typified by a resistive random access memory such as a resistance random access memory (ReRAM) and a phase-change random access memory (PRAM, registered trademark). However, the resistive random access memory using an existing access transistor results in an increased floor area per unit cell. Accordingly, as compared, for example, with a flash memory such as a NAND flash memory, it has not been easy to achieve the increase in capacity of a non-volatile memory even in a case where the non-volatile memory is miniaturized using the same design rules. In contrast, in a case where a so-called cross-point array structure is used, in which memory devices are provided at respective intersections (cross points) of intersecting wiring lines, a floor area per unit cell is reduced, thus making it possible to achieve the increase in capacity of the non-volatile memory.
A cross point memory cell is provided with a selecting device (a switch device) for cell selection, in addition to the memory device. Examples of the switch device may include a switch device (an ovonic threshold switch (OTS) device) using a chalcogenide material. In the OTS device, a leakage current is low in an OFF state; increasing a current in an ON state makes it possible to increase a selection ratio. Further, the OTS device exhibits switching characteristics, thus making it possible to obtain the selection ratio relatively easily even in a case where the OTS device is coupled in series to the memory device.
Note that a selector that includes a stacked body configured of a chalcogenide layer and an insulation layer is disclosed in PTL 1. In addition, a phase-change memory including a superlattice structure is disclosed in PTL 2. Further, a PRAM including a PN junction diode as a phase change diode is disclosed in PTL 3. Furthermore, a phase-change memory including an electrode that has a resistivity distribution is disclosed in PTL 4.